BIOENERGETICS TOPIC 4 CHANTELLE

• Autotrophs


  Plants that can make their own food using light, water and carbon dioxide
• Plants are called producers in food chains
• Photosynthesis


  An endothermic reaction in which energy is transferred from the environment to the chloroplasts by light

  
• Leaves


  • Where most photosynthesis takes place, in specialised mesophyll cells packed with chloroplasts containing chlorophyll to absorb as much light energy as possible

  
• The sugars produced by photosynthesis are used to make all the substances a plant needs, as well as being used in respiration to release energy

  
• Photosynthesis


  Carbon dioxide + Water + Light energy → Glucose + Oxygen

  
• Reactants for photosynthesis obtained by a plant

  • Light
  • Water
  • Carbon dioxide

  
• Water is not considered a limiting factor for photosynthesis as the amount needed is relatively small compared to the amount transpired from a plant

  
• Other environmental factors affecting photosynthesis rate

  • Temperature
  • Amount of chlorophyll in chloroplasts

  
• As temperature increases


  The rate of reaction increases
• At higher temperatures


  Enzymes that control photosynthesis can be denatured, reducing the overall rate

  
• As light intensity increases

  The rate of photosynthesis increases

  
• At a certain point

  Increasing light intensity stops increasing the rate as something else is limiting
• As carbon dioxide concentration increases

  The rate of photosynthesis increases

  
• As the number of chloroplasts increases

  The rate of photosynthesis increases

  
• Factors that can affect the amount of chlorophyll include diseases, lack of nutrients, and loss of leaves
• Interactions of limiting factors


  • More than one limiting factor can affect the rate of photosynthesis
  • Graphs may show the effect of two or three factors interacting

  
• Inverse square law


  Relationship between light intensity and distance - as distance increases, light intensity decreases

  
• Commercial horticulturists grow plants in greenhouses to control limiting factors of photosynthesis and maximise yield
• Spending money on increasing a factor beyond the point it limits photosynthesis is a waste

  
• Investigating photosynthesis in pondweed

  1. Measure oxygen produced as light intensity changes

  2. Calculate rates of photosynthesis

  3. Extract and interpret graphs

  
• Uses of glucose produced in photosynthesis

  • Respiration (aerobic and anaerobic)
  • Conversion to starch for storage
  • Production of fat/oil
  • Production of cellulose
  • Synthesis of amino acids and proteins

  
• A test to show a plant is photosynthesising is to test the leaf for the presence of starch using iodine
• Cellular respiration


  An exothermic reaction continuously occurring in living cells to release energy
• Aerobic respiration


  Glucose + Oxygen → Carbon dioxide + Water + Energy

  
• Anaerobic respiration in animals

  Glucose → Lactic acid + Energy

  
• Anaerobic respiration in plants and yeast

  Glucose → Ethanol + Carbon dioxide + Energy
• Comparison of aerobic and anaerobic respiration

  • Need for oxygen
  • Products
  • Energy transferred

  
• During exercise


  Breathing rate, breath volume, and heart rate increase to supply more oxygen to muscles
• If exercising vigorously


  Muscles use anaerobic respiration, producing lactic acid and creating an "oxygen debt"
• Metabolism


  The sum of all the reactions in a cell or the body, happening continuously
• Examples of metabolism


  • Conversion of glucose to cellulose, glycogen, lipids
  • Formation of amino acids and proteins
  • Breakdown of proteins to urea